Buy a one-way air ticket - especially to Europe - and you just may get fleeced, very possibly for thousands of dollars. That is the considered opinion of Patrick Surry, chief data scientist at Hopper whose specialty is crunching airfares. But can the consumer fight back and salvage some savings on pricey one-way tickets?

Surry called this expensive no-return booking phenomenon an “idiosyncracy” of the airfare market and added that Hopper had now built into its app a tool for comparing one-way fare data.

Such tools are needed, and others offer similar opportunities to save. Expedia, for instance, has offerings. What's more, multiple experts pointed to one-way fare finding tools at ITA Matrix Software by Google. In short, you need to price one-ways very carefully and choose your carrier with care as well. There are ways around the price gouging, and you simply need to educate yourself in order to outsmart the airline algorithms and price-setters.  

Tune into the numbers. Buy a roundtrip from Newark to Paris, leaving January 7, returning January 13 and Delta shows a price on Expedia of $906.60. The Delta one-way fare on January 7 is $2,606.80. That isn’t a misprint. The one-way price is dramatically higher than the roundtrip. That is no aberration, it’s the norm. Said Surry: “one-way flights are usually more expensive than round-trips.”

Travel expert Joe Brancatelli, who blogs at JoeSentMe, explained what is going on here: “The system at most airlines is that the cheapest fares are roundtrips. So if you're looking at a roundtrip fare and saying ‘I shouldn't pay more than half for a one-way,’ you misunderstand the way major carriers price their seats. Roundtrips allow them to sell cheaper, because they can load in day-of-stay restrictions that business travelers don't want to meet. I'm not endorsing what the airlines do, just noting why the cheapest fares on major airlines are usually roundtrips.”

When it crunched the numbers, Hopper found a one-way fare premium on European flights of 345.8% at Delta. But United topped that at 413.3%. In dollar terms the United premium averages out at $3,577. Per one-way ticket.

Domestic one-way premiums are high but not nearly as bad. United, per Hopper, has on average a 38.6% one-way premium on domestic flights. Delta has 25 percent.

So how do you not lose when flying one-way? And how do you do so without getting yourself into hot water?

The most prevalent frequent flyer tactic is to buy a roundtrip and throw away the return. Multiple travelers told us they do exactly that. One problem: doing so violates the so-called “conditions of carriage” at most domestic airlines.

Here is what American says, for instance: “American specifically prohibits practices commonly known as -- Throwaway ticketing: The usage of roundtrip excursion fare for one-way travel.” For its part, American contractually reserves a right to get even. It says it has the right to “refuse to board the passenger.”

Frequent flyers whispered they have not seen that. But do you want to count on the beneficence of an airline?

All the other legacy domestic carriers have similar contract language.

Which is why the shrewder tactic may be to hunt for carriers that impose no or minimal bumps for one-way fares. Such as? Hopper data fingers these domestic carriers as one-way friendly, said Surry: Spirit, Frontier, Alaska and JetBlue. The highest one-way premium of the bunch, per Hopper, is $17 at JetBlue, a tiny fraction of the upcharges at Delta and United.

Internationally, Hopper’s data is emphatic: forget the legacy carriers such as Delta, United, British Air, and Air France. The better deals, said Hopper, are with Norwegian Air Shuttle and Icelandair, often imposing little - or no - markup on one-way fares.

Frequent flyer Brad Chase, who blogs at TheTravelChase, corroborated this advice. “I’ve been through about 30 countries since 2010 mostly on one way tickets and have flown on one ways this year alone nearly 20 times,” Chase said. “The cost of one-way flights has been grossly exaggerated. While it’s true that it is usually significantly more expensive with many legacy airlines, all the dynamic and high-growth airlines are moving to à la carte pricing that doesn’t require a return ticket.”

Bottomline: price shop. Choose your carrier carefully. Be open to names that aren’t your usual carriers. And you can fly one-way at honest, decent rates. Said Dmitriy Dudarenko at AirfareSpot: “You may spend a little bit more time researching one-ways, but you can save a lot.”

This article is commentary by an independent contributor. At the time of publication, the author held TK positions in the stocks mentioned.